A drill chuck such as described in German patent document 3,727,147 for use with a tool having a shaft typically has a chuck body centered on and rotatable about an axis and an adjustment body centered on the axis, rotatable about the axis on the chuck body, and axially fixed on the chuck body. One of the bodies is formed with a plurality of angularly equispaced jaw-guide passages centered on respective jaw axes all lying on the surface of an imaginary cone centered on the axis. The other of the bodies is formed with a screwthread centered on the axis and exposed in the guide passages. Respective jaws displaceable in the passages along the respective axes are each formed with a row of teeth meshing with the screwthread so that relative rotation of the bodies in one direction moves the jaws radially inward and axially forward and opposite relative rotation moves the jaws radially outward and axially backward.
Such a chuck is often set up to be self-tightening by forming the passages in the adjustment body and is provided with a locking ring that is axially and limitedly angularly displaceable on the chuck body and engageable with teeth on the adjustment body to limit its rotation As the chuck is used the torque imparted to it tends to screw down the jaws, tightening them on the tool.
In U.S. Pat. No. 1,894,515 of Hubbel a nontightening chuck is described whose jaws are each formed with a generally axially extending entrainment ridge projecting radially inward and engaging the tool behind a plane drawn from the respective jaw axis to the chuck axis. Thus as the chuck is tightened the jaws are twisted in the passage to lock them all tightly in place with the ridges in a rear-pointing position. Thus when the chuck is used, however, the jaws are twisted all the way back, so that there is no tightening action and it is in fact fairly common for the tool to slip so that the chuck has to be retightened.